Q1

The default style is FLAT but this can be overridden to provide GRID which provides a better layout for preference pages.

Q2

There are many subclasses of FieldEditor, which include editors for Boolean, Color, Combo, Font, List, RadioGroup, Scale, String, Integer, Directory, and File.

Q3

To provide searching in a preference page, keywords must be registered via the extension point.

Q4

Don't use IMemento for anything. Use anything else including IEclipsePreferences or DialogSettings.

Q5

The MessageDialogWithToggle class provides the "Do not show this message again" support.